Portable radio equipment



1 ENTOR Ian/#AMV Filed Sept. 6, 1940 Patented Sept. 29, 1942 PORTABLE RADIO i EQUIPMENT Walter Kuhlmann, Brunswick, Germany; vested in the Alien Property Custodian Application September 6, 1940, Serial No. 355,567 In Germany July 10, 1939 (Cl. Z50-13) 4 Claims.

This invention relates to radio apparatus of the kind comprising a transmitter and a receiver which are operated either on the same wavelength or on different wavelengths, these wavelengths in most cases being in the neighbourhood of each other.

In many cases such apparatus is in the form of easily portable knapsack equipment. In this equipment the provision of a long-life current supply is often difficult. Therefore, in order to save the current sources it has been proposed that the well-known methods of energy-saving modulation be adopted in this equipment, these methods having been formerly employed only with stationary radio stations, especially broadcast transmitters. According to these methods, the working point and hence the output of one or more stages of the transmitter is varied above a predetermined idle value.

The invention is concerned with the constructional arrangement of the above-mentioned portable equipment. According to the invention, the receiver is as a whole or in part utilized for effecting the working point control, that is, the said energy-saving modulation.

In the case of the invention the expenditure in apparatus is not greater than it is usually. All the parts of such apparatus are dimensioned to be worked at their full load capacity. In order to control the working point and thereby to obtain an energy-saving modulation a certain control power must be produced. For this purpose a continuous voltage is derived from the modulation currents and is caused, after passing through an amplier, to so influence the grid circuit of a stage of the transmitter, or a screening grid circuit thereof, that the working point of the stage shall be displaced in accordance with the modulation amplitudes, Methods of this kind are known as floating carrier modulation. To properly control the transmitter a certain energy must be delivered by the said amplifier. Such additional energy is not of importance as far as the overall energy saving is concerned in View of the gain in energy obtained by the iioating carrier modulation.

With stationary radio stations the added apparatus required by the provision of an amplifier does not require consideration. Such is not the case, however, where portable equipment is concerned, in which the total amount of apparatus should be kept low as far as possible. In addition, special diculties arise when it is desired to arrange additional ampliers in apparatus manufactured by mass production, or in standardized commercial apparatus.

These disadvantages are overcome by utilizing the receiver either as a whole or in part for controlling the working point in the manner peculiar to the invention. While on the one hand the total amount of apparatus is not increased, it is on the other hand also possible to elect the said saving of energy in standardized commercial apparatus without the addition of amplifier stages.

The invention is described hereafter with reference to the accompanying drawing, which shows the circuit arrangement of one embodiment thereof. Only such parts are represented as are necessary for understanding the invention,

Depending upon the position of armature K1 of relay I either the transmitter, shown on the left in the drawing, or the receiver, shown on the right in the drawing, is connected to the antenna A. In the normal position of armature K1 the antenna A is connected to the receiver, and when the relay I is energized, the antenna is connected to the transmitter.

The transmitter comprises two stages, namely, a control stage having an electron tube 2 and an output stage having an electron tube 3. As shown, tubes 2 and 3 are four-element tubes having cathodes 2l and 22, control grids 23 and 24, screen grids 25 and 26, and anodes 21 and 28, but they may also be pentodes if desired. The control stage may be either a high frequency oscillator or a conventional amplier controlled by a separate high frequency source. The output stage is a conventional amplier, and the two stages may be coupled by any well known means.

The receiver comprises three stages 5, 6 and l, stages 5 and 6 being coupled by any Well known means. lThese stages are the usual stages of an ordinary portable receiver. Stage 'l is coupled to stage 6 by a transformer I6 and to the audio reproducer 8 by a transformer Il.

The arrangement shown in the drawing may be used for both telephony and telegraphy. When it is used for telegraphy, keying is effected by means of key 9. With switch ll in the position shown, as is required for telegraphic operation, the screen grids 25 and 26 are connected to the left hand Contact associated with armature K10. Armature K10 is against the right hand when winding Ill is not energized. When key 9 is pressed, windings l and l0 are energized pulling armatures K1 and K10 to the left and thereby applying potential to anodes 21 and 28 and grids 25 and 26. At the same time the antenna A is connected to the output stage. With the application of the potential to the electrodes of tubes 2 and 3, the transmitter becomes operative to produce oscillations and energizes the antenna thus producing radiations from the antenna. With manipulation of the key 9 corresponding radiations are produced.

When the arrangement shown in the drawing is used for telephony, modulation of the transmitter is eiiected by the microphone 4. As in telegraphic operation the key 9 must be pressed, that is, key 9 in this case acts as a push-totalk key as is usual in portable equipment of the present kind. When the key 9 is pressed, relays I and IU operate as before to connect the antenna to the transmitter and to apply potential to the anodes 2l and 28. However, with telephonie operation the switch I I is reversed and screen grids 25 and 26 are not energized from the same source as the anodes 21 and 28, but instead they are energized over line from the network I3, I4, I9 and I9 where I3 is a condenser, I4, a resistance, I8, a transformer, and I9, a rectifier. A residual or at rest screen grid voltage is applied to the screen grids through the resistance I4 which is connected to a D. C. voltage source (not shown) during periods that the carrier is unmodulated. The screen voltage produced is relatively small, and hence the carrier power and energy drain on the power source is low. By speaking into the microphone 4 which is coupled to the screen grids by transformer I2, an additional voltage is produced at capacity I3 and resistance I4. This resulting additional voltage is produced by conveying the modulating voltage in the anode circuit of tube 3 over transformer I6 to the stage 'I in which it is ampliiied. The output voltage of stage 1 corresponding to the modulating voltage is rectified as before, and an additional voltage corresponding to the mean variations of the sound intensity at the microphone appears across elements I3 and I4. None of the modulating voltage is conveyed to the reproducer 8 because armature K1 which is operated by relay I short circuits the primary winding of transformer I'I. The Voltage that appears at the resistance I4 due to the modulating voltage is conveyed to the screen grids and 26 of the transmitter stages over the line 23, and thus the high frequency power of the transmitter is varied in accordance with the mean modulating or speech voltage,

The arrangement here disclosed renders it possible with an unmodulated carrier value of 40% to obtain a saving of about 60%, and with a mean modulation of to obtain a saving in the battery output of about to 50%. The life of the anode battery thus doubles, If an unmodulated value of the carrier is not utilized, the operation then being based on a value equal to zero, the battery saving may be still further increased without impairing the intelligibility too much.

What is claimed is:

1. Portable radio apparatus comprising a transmitter and a receiver, means for alternatively operating said transmitter and receiver, means in said transmitter for producing amplitude modulation of the output of said transmitter and means in said receiver for further amplitude modulating the output of said transmitter in accordance with the amount of said firstmentioned modulation.

2. Portable radio apparatus comprising a transmitter having means for producing a carrier voltage, means for producing a modulating voltage, and means for amplitude modulating said high frequency voltage, a receiver having amplifying means, means for selectively operating said transmitter and said receiver, means for conveying a portion of said modulating voltage to said amplifying means, rectifying means coupled to said amplifying means for producing a rectiiied voltage proportional to the mean value of said modulating voltage, and means for further amplitude modulating said carrier voltage by said rectified Voltage.

3. Portable radio apparatus comprising a transmitter having means for producing a carrier voltage, means for producing a modulating voltage and modulating means coupled to said means for producing amplitude modulated carrier waves, a receiver having an amplier, rectifying means coupled to said ampliiier, means for coupling said modulating means to said ampliiier, means for coupling said rectifier to said modulating means, and means for selectively operating said transmitter and said receiver.

4. Portable radio apparatus comprising a transmitter comprising a source of carrier voltage, an ampliiier having a tube comprising a cathode, a control grid, a screen grid and an anode, said amplifier being coupled to said source, a source of modulating voltage coupled to said screen grid and means for radiating radio frequency energy coupled to saidamplier, a receiver comprising an ampliiier, means for coupling said receiver ampliiier to said transmitter amplifier, rectifying means coupled to said receiver amliiier, means for coupling said rectifying means to said screen grid, and means for selectively operating said transmitter and said receiver.

WALTER KUHLMANN. 

